Aromatic amines having unsubstituted hydrogen atoms in positions ortho to amino groups may be alkylated in the ortho position in a number of ways.
Kolka, et al, U.S. Pat. No. 2,814,646, describes alkylation of aromatic amines having unsubstituted ortho positions by reacting the aromatic amine with an aliphatic olefin in the presence of an aluminum trianilide catalyst. The aromatic amine may have additional substituents provided that there is an unsubstituted position ortho to an amino group available for alkylation.
The catalyst of Kolka, et al, is prepared in a process which reacts the aromatic amine, having at least one hydrogen bonded to the amino nitrogen, with aluminum metal, aluminum alkyl, aluminum amide, and the like. Between about 0.1-20% of the aromatic amine is converted to the aluminum anilide type catalyst. The Kolka, et al, process may be conducted between the temperatures of about 250.degree. C. up to decomposition temperature, e.g., 400.degree. C., under olefin pressure.
Stroh, et al, U.S. Pat. No. 3,275,690, is an improvement over the Kolka, et al, process by including a small amount of Friedel-Crafts catalyst as a promoter. Stroh, et al, mentions aluminum chloride, aluminum bromide, iron chloride, boron trifluoride, zinc chloride, stannic chloride, and the like as examples of promoters. The amount of promoter used is disclosed to be between 0.05 and 10 wt. % of the amount of aromatic amine utilized. The alkylation temperature is between about 150.degree. C. and about 400.degree. C. under olefin pressure.
Klopfer, U.S. Pat. No. 3,923,892, provides a similar method of ortho alkylation of aromatic amines utilizing an alkyl aluminum halide catalyst, such as diethylaluminum chloride or ethylaluminum sesquichloride. The amount of catalyst required provides about one gram atom of aluminum per each 5-40 gram moles of aromatic amine. A portion of the aluminum may be provided by reacting aluminum metal with the aromatic amine.
Governale, et al, U.S. Pat. No. 4,128,582, describes a process of selective ortho-alkylation of aromatic amines using an aluminum anilide catalyst in which the reaction rate is increased by addition of a hydrogen halide to the alkylation mixture. The process is conducted by reacting an aromatic amine with an olefin in the presence of the aluminum anilide catalyst at a temperature of between about 200-500.degree. C. A hydrogen halide may be added to the reaction mixture as a promoter in an amount to provide up to two halogen atoms per aluminum atom.